CN101964608A - Photovoltaic power generation distribution type maximum power output system - Google Patents

Abstract

The invention provides a distributed maximum power output system for photovoltaic power generation, comprising: a solar energy collection device including more than two sets of photovoltaic module groups, the photovoltaic module collects solar energy and converts the solar energy into DC power and sends it to the front-stage control module; the front-stage control module The module string group includes more than 2 groups of front-level control modules that correspond to the photovoltaic modules one by one and are set in series. The front-level control module outputs current to the rear-level control module after voltage conversion; The latter control module, the latter control module converts the DC voltage and sends it to the inverter conversion module; the inverter conversion module outputs the current. The present invention adopts the current and voltage two-level control mode, this control structure eliminates the influence between adjacent modules, the photovoltaic modules in the same group have no influence on each other, and there is no need to obtain the information of adjacent modules, which simplifies the output control of the modules , which improves the stability and reliability of the power output control and power generation system.

Description

A distributed maximum power output system for photovoltaic power generation

technical field

The invention relates to a photovoltaic power generation distributed maximum power output system.

Background technique

The basic unit of a photovoltaic power generation system is a photovoltaic module. The photoelectric characteristics of photovoltaic modules are nonlinear, and there are peaks in their power curves. Therefore, a large number of maximum power point tracking (MPPT) methods have been proposed to ensure the maximum power output of photovoltaic modules. A photovoltaic system consists of multiple photovoltaic modules connected in series and parallel to form a photovoltaic array. Under uniform light conditions, the power curves of each photovoltaic module are consistent, and the power curve of the photovoltaic array has a unique peak. Under partial shade conditions, the power curves of each photovoltaic module are different, and the power curve of the photovoltaic array appears multi-peak phenomenon. At this time, the photovoltaic power generation system may not output the maximum power.

Among various MPPT technical solutions, they can be divided into centralized MPPT and distributed MPPT. The practice of the centralized MPPT scheme is to compensate according to the comprehensive effect of the entire photovoltaic panel array. The method of the distributed MPPT scheme is to perform independent compensation according to the individual output of each photovoltaic module. At this time, the output power of each solar panel is maximized, so distributed MPPT is the most promising technology to improve the energy productivity of solar power generation systems. The current power output control structure is shown in Figure 1. Each photovoltaic module is connected in series with a DC voltage conversion module and then connected in parallel, and the parallel connected photovoltaic modules and DC voltage conversion module are connected in series with an AC/DC voltage conversion module. In this structure, the current value and voltage value both change during the process of voltage conversion and output power, which causes the photovoltaic modules in the same group to affect each other. It is necessary to obtain the information of adjacent modules, and the adjacent modules will affect each other. In order to balance the power output of each module, very complex output control is required. The complexity of output control not only increases the control cost, but also seriously affects the reliability and stability of the control, thereby affecting the stability and reliability of the power generation system.

Contents of the invention

The technical problem to be solved by the present invention is to provide a photovoltaic power generation distributed maximum power output system with simple power output control, reliability and high stability.

In order to solve the above problems, the present invention provides a distributed maximum power output system for photovoltaic power generation, including:

Solar energy collection device, the solar energy collection device includes more than 2 sets of photovoltaic module groups, each photovoltaic module in the photovoltaic module group is connected with a front-level control module, and the photovoltaic module collects solar energy and converts the solar energy into DC power for transmission to the front-end control module;

A front-end control module string group, the front-end control module string group includes more than two groups of front-end control modules corresponding to the photovoltaic modules one by one and arranged in series, and the front-end control module receives the information sent by the photovoltaic module After the direct current power, the voltage conversion is performed under the condition of a fixed current value, and the current of the maximum power value is respectively output to the subsequent control module;

The rear-stage control module group, the latter-stage control module group includes more than 2 rear-stage control modules arranged in parallel, and the latter-stage control module is connected to receive the current input by the front-stage control modules arranged in series in each group, and performs direct current After the voltage is transformed, it is sent to the inverter conversion module;

An inverter conversion module, the inverter conversion module is connected to receive the current input by each subsequent control module arranged in parallel in the subsequent control module group, and converts the direct current into an alternating current for output.

Further, the front-end control module includes:

A first filter unit, the first filter unit receives the current sent by the photovoltaic module, filters it and sends it to the voltage conversion unit;

A voltage conversion unit, the voltage conversion unit receives the current sent by the first filter unit, performs voltage conversion under the control of the tracking control unit, and then sends it to the second filter unit;

A second filter unit, the second filter unit receives the current sent by the voltage conversion unit, filters it and sends it to the output unit;

an output unit, the output unit receives the current sent by the second filter unit and outputs it;

A tracking control unit, the tracking control unit collects the voltage and current parameters of the photovoltaic module and the voltage parameters of the output unit, and controls the action of the voltage conversion unit according to the linear change of the maximum fixed output power of the current value.

Further, the tracking control unit includes:

A measurement subunit, the measurement subunit measures the voltage value and current value of the photovoltaic module, and sends them to the control subunit in the form of parameters;

a feedback subunit, the feedback subunit tracks and monitors the voltage value of the output unit, and sends it to the control subunit in the form of a parameter;

A control subunit, the control subunit receives the parameter values sent by the measurement subunit and the feedback subunit, controls each parameter when calculating the maximum power output according to the set current value, and sends the parameters to the adjustment subunit;

An adjustment subunit, the adjustment subunit receives the control parameters sent by the control subunit, adjusts the value of each parameter according to the duty cycle limit, and controls the action of the voltage conversion unit according to the adjusted parameter value.

Further, an intelligent protection unit is connected between the second filter unit and the output unit, and the intelligent protection unit receives the current sent by the second filter unit for testing and compares it with the set protection value Yes, sent to said output unit after taking corresponding action.

Further, the intelligent protection unit includes:

A test subunit, the test subunit tests the voltage and current parameters of the photovoltaic module and the voltage parameters of the output unit, and sends the tested data to the judgment subunit;

A judging subunit, the judging subunit receives the data sent by the testing subunit, compares it according to the preset protection parameters, and controls the action of the on-off subunit according to the comparison result;

An on-off subunit, the on-off subunit connects and disconnects the circuit between the second filtering unit and the output unit under the control of the judging subunit.

The present invention has the following advantages:

1. The present invention adopts a two-stage control mode of current and voltage. The front-stage control module uses a fixed current method to control the photovoltaic modules connected in series; the rear-stage control module uses a fixed voltage method to control the parallel-connected photovoltaic module groups. This control structure eliminates the influence between adjacent modules, and the photovoltaic modules in the same group have no influence on each other, and do not need to obtain the information of adjacent modules, which simplifies the output control of the modules, improves the power output control and the stability of the power generation system sex and reliability.

2. The tracking control unit in the present invention has a simple structure, can effectively track various parameters of input and output currents, perform online compensation and correction, improve power output efficiency, and ensure power output stability.

3. The present invention also adopts an intelligent protection unit, which can judge the state of parameters such as open circuit voltage, short circuit current and panel temperature, so as to provide protection for the photovoltaic module, improve the reliability and self-protection function of the photovoltaic power generation system, and reduce unnecessary losses .

4. The structure of the present invention is simple, reliable and high in stability. The present invention relies on rational structure to reduce cost and operational difficulty, and is easy to popularize and apply.

Description of drawings

Embodiments of the present invention will be further described below in conjunction with accompanying drawings:

FIG. 1 shows a schematic diagram of a current power output control structure;

Fig. 2 shows a schematic structural diagram of a photovoltaic power generation distributed maximum power output system according to the present invention.

Detailed ways

As shown in FIG. 2 , the present invention includes a solar energy collection device 1 , a front-stage control module string group 2 , a rear-stage control module group 3 and an inverter conversion module 4 . The solar energy harvesting device 1 is used to collect solar energy. It achieves the maximum power output through the two-stage control of the front-stage control module string group 2 and the rear-stage control module group 3 , and then performs current output through the inverter conversion module 4 after current conversion.

The solar energy harvesting device 1 includes more than two sets of photovoltaic module groups 11, each photovoltaic module 111 in the photovoltaic module group 11 is connected with a front-end control module 21, and the photovoltaic module 111 collects solar energy and converts the solar energy into DC power and sends it to the front-end control Module 21.

The front-end control module string group 2 includes more than two sets of front-end control modules 21 that correspond to the photovoltaic modules 111 and are arranged in series. After the front-end control modules 21 receive the DC power sent by the photovoltaic modules 111, Next, the voltage conversion is performed, and the current with the maximum power value is output to the subsequent control module 31 respectively.

The rear-stage control module group 3 includes more than two rear-stage control modules 31 arranged in parallel, and the latter-stage control module 31 is connected to receive the current input by each group of series-connected front-stage control modules 21, convert the DC voltage and send it to the inverter for conversion Module 4.

The inverter conversion module 4 is connected to receive the current input by each rear-stage control module 31 arranged in parallel in the rear-stage control module group 3 , and converts the direct current into an alternating current for output.

The present invention adopts two-level control modes of current and voltage. The front-stage control module 2 uses a fixed current method to control the photovoltaic modules connected in series; the rear-stage control module 3 uses a fixed voltage method to control the parallel-connected photovoltaic module groups. This control structure eliminates the influence between adjacent modules, and the photovoltaic modules 111 in the same group have no influence on each other, and there is no need to obtain the information of adjacent modules, which simplifies the output control of the modules, and improves the power output control and power generation system. stability and reliability.

In the present invention, the pre-stage control module 21 includes a first filter unit 211 , a voltage conversion unit 212 , a second filter unit 213 , an output unit 214 and a tracking control unit 215 . The first filtering unit 211 and the second filtering unit 213 are used for filtering, the voltage conversion unit 212 is used for voltage conversion, the output unit 214 is used for outputting current, and the tracking control unit 215 is used for controlling voltage conversion to achieve maximum output power.

Both ends of the first filter unit 211 are respectively connected to the photovoltaic module 111 and the voltage conversion unit 212 , the first filter unit 211 receives the current sent by the photovoltaic module 111 , filters it and sends it to the voltage conversion unit 212 .

Both ends of the voltage conversion unit 212 are respectively connected to the first filter unit 211 and the second filter unit 213 , and the voltage conversion unit 212 is also controlled 215 by the tracking control unit. The voltage converting unit 212 receives the current sent by the first filtering unit 211 , and sends the current to the second filtering unit 213 after performing voltage conversion under the control of the tracking control unit 215 .

Both ends of the second filter unit 213 are respectively connected to the voltage conversion unit 212 and the output unit 214 , the second filter unit 213 receives the current sent by the voltage conversion unit 212 , filters it, and then sends it to the output unit 214 .

The output unit 214 receives the current sent by the second filtering unit 213 and outputs it.

The tracking control unit 215 collects the voltage and current parameters of the photovoltaic module 111 and the voltage parameters of the output unit 214, and controls the action of the voltage conversion unit 212 according to the linear change of the maximum fixed output power of the current value.

In the present invention, the tracking control unit 215 further includes a measurement subunit 2151 , a feedback subunit 2152 , a control subunit 2153 and an adjustment subunit 2154 . in:

The measurement subunit 2151 measures the voltage value and current value of the photovoltaic module 111 and sends them to the control subunit 2153 in the form of parameters.

The feedback subunit 2152 tracks and monitors the voltage value of the output unit 214 and sends it to the control subunit 2153 in the form of a parameter.

The control subunit 2153 receives the parameter values sent by the measurement subunit 2151 and the feedback subunit 2152 , controls each parameter when calculating the maximum power output according to the set current value, and sends the parameters to the adjustment subunit 2154 .

The adjustment subunit 2154 receives the control parameters sent by the control subunit 2153 , adjusts the values of the parameters according to the duty ratio limit, and controls the voltage conversion unit 212 to operate according to the adjusted parameter values.

The tracking control unit 215 in the present invention has a simple structure, can effectively track various parameters of input and output currents, perform online compensation and correction, improve power output efficiency, and ensure power output stability.

In the present invention, an intelligent protection unit 216 is also connected between the second filter unit 213 and the output unit 214, and the intelligent protection unit 216 receives the current sent by the second filter unit 213 for testing and compares it with the set protection value , and send it to the output unit 214 after taking corresponding measures.

The intelligent protection unit 216 in the present invention includes a testing subunit 2161 , a judging subunit 2162 and an on-off subunit 2163 . in:

The testing subunit 2161 tests the voltage and current parameters of the photovoltaic module 111 and the voltage parameters of the output unit 214 , and sends the tested data to the judging subunit 2162 .

The judgment subunit 2162 receives the data sent by the test subunit 2161, compares it according to the preset protection parameters, and controls the on-off subunit action 2163 according to the comparison result. In the judging subunit 2162 , refer to historical data and mathematical models to perform data prediction and threshold setting, thereby making fuzzy judgments and sending corresponding action instructions to the on-off subunit 2163 .

The on-off subunit 2163 connects and disconnects the circuit between the second filtering unit 213 and the output unit 214 under the control of the judging subunit 2162 .

The present invention also adopts an intelligent protection unit 216, which can judge the state of parameters such as open circuit voltage, short circuit current and panel temperature, thereby providing protection for the photovoltaic module 111, improving the reliability and self-protection function of the photovoltaic power generation system, and reducing unnecessary losses .

The invention has simple structure, reliability and high stability, and the invention relies on rational structure to reduce cost and operation difficulty, and is easy to popularize and apply.

In summary, the above are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention, All should be included within the protection scope of the present invention.

Claims (5)

1. A distributed maximum power output system for photovoltaic power generation, characterized in that it comprises: A solar energy collection device (1), the solar energy collection device (1) includes more than 2 groups of photovoltaic module groups (11), and each photovoltaic module (111) in the photovoltaic module group (11) is connected with a front-level control module ( 21), the photovoltaic module (111) collects solar energy and converts the solar energy into DC power and sends it to the front-end control module (21); A front-end control module string (2), the front-end control module string (2) includes more than two groups of front-end control modules (21) corresponding to the photovoltaic modules (111) and arranged in series, the After the front-stage control module (21) receives the DC electric energy sent by the photovoltaic module (111), it performs voltage conversion under the condition of a fixed current value, and outputs the current of the maximum power value to the rear-stage control module (31) respectively; The rear-stage control module group (3), the latter-stage control module group (3) includes more than 2 rear-stage control modules (31) arranged in parallel, and the rear-stage control module (31) is connected to receive each group of series-connected The current input by the pre-set control module (21) is sent to the inverter conversion module (4) after DC voltage conversion; An inverter conversion module (4), the inverter conversion module (4) is connected to receive the input current of each rear-stage control module (31) connected in parallel in the rear-stage control module group (3), and converts the direct current into Output after alternating current. 2. The distributed maximum power output system of photovoltaic power generation as claimed in claim 1, characterized in that: the front-end control module (21) includes: A first filter unit (211), the first filter unit (211) receives the current sent by the photovoltaic module (111), filters it and sends it to the voltage conversion unit (212); A voltage conversion unit (212), the voltage conversion unit (212) receives the current sent by the first filter unit (211), performs voltage conversion under the control of the tracking control unit (215) and then sends it to the second filter unit (213 ); A second filter unit (213), the second filter unit (213) receives the current sent by the voltage conversion unit (212), performs filtering, and then sends it to the output unit (214); an output unit (214), the output unit (214) receives the current sent by the second filter unit (213) and outputs it; A tracking control unit (215), the tracking control unit (215) collects the voltage and current parameters of the photovoltaic module (111) and the voltage parameters of the output unit (214), and controls the The voltage conversion unit (212) operates. 3. The distributed maximum power output system of photovoltaic power generation as claimed in claim 2, characterized in that: the tracking control unit (215) comprises: The measurement subunit (2151), the measurement subunit (2151) measures the voltage value and current value of the photovoltaic module (111), and sends them to the control subunit (2153) in the form of parameters; A feedback subunit (2152), the feedback subunit (2152) tracks and monitors the voltage value of the output unit (214), and sends it to the control subunit (2153) in the form of parameters; The control subunit (2153), the control subunit (2153) receives the parameter value sent by the measurement subunit (2151) and the feedback subunit (2152), and calculates the control parameter at the time of maximum power output according to the set current value , and send this parameter to the adjustment subunit (2154); An adjustment subunit (2154), the adjustment subunit (2154) receives each control parameter sent by the control subunit (2153), and adjusts each parameter value according to the duty cycle limit, and controls according to the adjusted parameter value The voltage conversion unit (212) operates. 4. The photovoltaic power generation distributed maximum power output system according to claim 3, characterized in that: an intelligent protection unit (216) is also connected between the second filtering unit (213) and the output unit (214) ), the intelligent protection unit (216) receives the current sent by the second filter unit (213) for testing, and compares it with the set protection value, and sends it to the output unit (214) after taking corresponding measures . 5. The distributed maximum power output system of photovoltaic power generation as claimed in claim 4, characterized in that: the intelligent protection unit (216) comprises: A test subunit (2161), the test subunit (2161) tests the voltage and current parameters of the photovoltaic module (111) and the voltage parameters of the output unit (214), and sends the tested data to the judgment subunit (2162 ); A judging subunit (2162), the judging subunit (2162) receives the data sent by the testing subunit (2161), compares it according to preset protection parameters, and controls the on-off subunit (2163) according to the comparison result )action; An on-off subunit (2163), the on-off subunit (2163) connects and disconnects the circuit between the second filtering unit (213) and the output unit (214) under the control of the judging subunit (2162) .

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